Transfer method and means



s E w s L B TRANSFER METHOD AND MEANS H ling m y n [I al pro '7, 1936man ,AT E N T l 2,0dhb35 TRANSFER Benia 1L. Sites, @hieago, designer toThe Miehle Printing ess and ltdanufactng @opany, iflhicago, Hill, acorporation of ois Application December 0, i933, Serial lilo. 701,412llll dam, (oi. rot-ire) purpose of transferring a printing image withoutmade of rubber, gelatin, or other compositions.

Mechanisms of this nature would include inking mechanism of printingpresses which embo'dy series of ink distributing rollers, some of whichare of steel and others of a flexible substance, some of the latterrollers being in contact with the steel rollers in order to distributethe ink, while others are arranged to contact with a printing form forthe purpose of applying a film of ink thereto.

A particularly advantageous application of my invention would be inconnection with a pianographic offset printing press in which a rubberblanket is used to transfer an impression from a planographic printingplate to the paper, that is to say, instead of effecting an impressiondirect from the printing plate onto the material to be printed, animpression is, first transferred from the inked plate to the rubberblanket, which then applies the impression to the print receivingmaterial.

- While the usefulness of the invention may be extended to any type ofoffset press it is more advantageously applied in connection with therotary type of planographic offset press, the printing units of whichinclude a form cylinder having a hard surface, a transfer or blanketcylinder having a resilient surface, and an impression cylinder having ahard surface.

Accordingly I have elected to describe and illustrate my invention asembodied in a planegraphic press of the latter class.

Heretofore, in preparing presses of this class for printing, it has beencommon practice to so dimension said cylinders by packing or otherwise,that their peripheral i. e. gear pitch line diameters were identical.

It is also a well established procedure in presses of this class to'packone or the other, or both of the complementary cylinders severalthousandths of an inch above their bearers, i. e. above their gear pitchlines, in order to attain the squeeze necessary for eflecting animpression. For instance, in making rotary offset presses ready forprinting, it has been known to pack the plate cylinder .001 inch, theblanket cylinder .002 inch to .003 inch, and the impression cylinder.002 inch above their bearers. Other proportional thicknesses ofpackings have been resorted to, which thicknesses varied depending onthe prevailing conditions, such as the gauge and structure of the stockto be printed, the quality of the ofiset blanket to be used, etc. Themotive of all the packing methods heretofore used, however, is the same,namely that of attaining the necessary impression for printing.

1 have ascertained that when, under any of the above conditions, theimpression is effected from a resilient surface, as is the case inofiset printing, the subject very often prints long, that is to say, thelength of the printed matter or desimi is in excess of that of thedesign on the form or plate, and the dots of halftone printing show aslight elongation. Such conditions are exceedingly undesirable,particularly so inmulticolor work where accurate register of thesuccessive impressions is essential, or in printing articles such asscales and other measuring implements where a variation in the divisionsis not permissible.

In order to definethe cause of this variation with a view to eliminatingthe inherent defects, I have made very careful observations and haveanalyzed the prevailing conditions as follows:

In rotary printing presses, where two or more cylinders are in rollingcontact with each other for the purpose of effecting impressions onpaper or other material, it is desirable to establish true rollingbetween the cylinder surfaces in order to obtain satisfactory printingresults. In the case where the contacting cylinder surfaces are made ofnon-resilient material, it is not difilcult to maintain true rolling.However, when the surface of one of the contacting cylinders is made ofhard i. e. non-resilient material, and the surface of the complementarycylinder is of a resilient substance, such as rubber, then the problemof attaining true rolling becomes a difficult one.

I- have found that when the normal diameter of two cooperatingcylinders, one of which has a hard surface and the other a resilientsurface, are the same, then the effective diameter of the cylinder withthe resilient surface, when in rolling contact with the other cylinderand when under the two contacting cylinders, also to some degree on thenature of the material which constitutes the resilient surface.

This fact I have proven by the following simple experiment:

A roller with a coating of composition having a thickness of inch andthe roller having a total diameter of 0.8 inch, was rolled over a flatsurface and by suitably marking the roller periphery, it was ascertainedthat when the composition was not compressed during the rolling of theroller over said surface, the roller traveled 2.5 inches per revolution;however, when during rolling, the composition coating was compressed tohalf its normal thickness, then the roller traveled 2.75 inches. Inother words, compressing of the composition coating to half its normalthickness added about 10 per cent to the diameter of the roller at itspoint of contact with a solid or non resilient surface.

It will be readily understood therefore, that if a similar conditionprevails in an offset press, the quality of printing will be seriouslyimpaired, the main cause for this being that due to the increase of theeffective or working diameter of the blanket cylinder at the printingzone, a certain amount of slippage takes place when the material to beprinted passes between the blanket cylinder and the impression cylinder,which latter, due to its hard surface, of course retains its normaldiameter. slippage of this nature, besides the fact that it will causethe subject to print long, is probably also responsible for suchprinting defects as smudging, gear streaks, inaccurate register andothers.

As indicated above, the fundamental elements of an offset press arethree cylinders, namely a plate cylinder which carries the printingplate or form, a blanket cylinder which is provided with a resilientblanket to receive an impression from the form, and an impressioncylinder, the surface of which latter might be bare metal or if desired,might be covered with a suitable non-resilient packing. All of thesecylinders are provided with bearers and intermeshing gears which areessential elements in printing presses of this class, the bearers of theplate cylinder under normal conditions being in rolling contact with thebearers of the blanket cylinder, and the bearers of the latter in turnbeing in rolling contact with the bearers of the impression cylinder.

These bearers necessarily are of equal diameters, which correspond withthe pitch line diameters of the respective gears arranged on eachcylinder for driving them. Assuming that there is no back lash betweenthe intermeshing gears, namely between the gears of the plate, blanketand impression cylinders, then no slippage will be possible between thebearers on the respective cylinders. In other words, there will be atrue rolling condition between the bearers, and consequently the surfacespeed of all cylinders will be equal, because, as stated herein,according to common practice, the plate, blanket and impressioncylinders are so dimensioned that their peripheral i. e. gear pitch linediameters are identical. Theoretically, therefore, there should be noslippage of the material to be printed and the dimension of theimpression thereon should be identical with that of the design orsubject on the printing plate.

However, as explained above, in order to effect a printing impression,it is essential that pressure, .commonly termed in the trade -squeeze",be applied at the printing zone, that is to say, at the aoaaaes point ofcontact between the cooperating members of a printing unit, which, incase of an offset press, would be between the blanket cylinder and theimpression cylinder, as well as between the blanket cylinder and theplate cylinder. Therefore, due to the compression and consequentdisplacement of the resilient material, namely the rubber blanket on theblanket cylinder, the efiective diameter of the latter, as proven by theexample given above, will increase and consequently the impressiontransferred from the plate cylinder to the blanket cylinder and thenfrom the blanket to the material to be printed, will print long.

With a view to eliminating this condition, which among other defectscauses a variation in the dimensions of the printed subject, I havecarried out extensive experiments which proved the necessity of avoidingany slippage of the material at the printing zone and of establishing atrue rolling condition between the surfaces of the cooperating printingmembers at the printing zone in order that it may be possible to obtaintrue impressions, the size of which coincide exactly with the image onthe printing plate or form. Furthermore, I found that the difficulticsheretofore experienced with smudging, etc. will be effectively overcomewhen true rolling between the printing members is maintained.

In view of the fact that the surface speed of the blanket cylinder atits printing zone, that is to say, at its points of contact with theplate and impression cylinders, increases due to the conditionsexplained above and as proven by my tests, it is evident that in orderto avoid any distortion of the printing image and any slippage of thematerial during printing, the surface speed of the impression cylinderas well as of the plate cylinder should be correspondingly increased.This I propose to accomplish by making the diameters of the latter twocylinders appreciably larger than the diameter of the blanket cylinder,while preferably I under pack the blanket cylinder so that the printingsurface of the blanket will be below the bearers of the blanketcylinder. The proportions of the respective diameters being such thatunder non-printing conditions the surface speed of the plate andimpression cylinders will be greater than that of the blanket cylinder,while under printing conditions the surface speed at the printing zoneof these cylinders will be identical.

I realize, however, that an increase in the surface speed of saidcylinders could be made possible by other methods, and therefore I donot wish to limit myself to the specific feature of increasing thediameters of the cylinders for the purpose of correspondingly increasingtheir surface speed.

In order to more clearly disclose the objects of my invention, I haveillustrated the above referred to conditions in the accompanyingdrawing, in which:

Figure 1 shows the general arrangement of an offset press in connectionwith which my invention may be applied to advantage;

Figure 2 shows the distortion of the resilient material on a'printingroller when rolled under pressure over a non-resilient flat surface;

Figure 3 indicates to an exaggerated extent the condition which arisesin an ofiset press when pressure is applied at the printing zone betweenthe respective printing cylinders;

Figure 4 gives an enlarged view of the distorted portion shown in Figure3 of a printing blanket at the point of contact between the blanketcylinder nuances and the impression cylinder of a printing press; and

Figure 5 illustrates diagrammatically a formcylinder, blanket cylinderand an impression cylinder with their bearers and associated gears.

Referring now more specifically to Figure l,

which shows in diagrammatic elevation the prin-' cipal elements of asingle color ofiset press, in

which, for the purpose of illustration, the sheet" it is shown as havingbeen fed down over the feed board ii to grippers if of the impressioncylinder it. In the vicinity of the plate cylinder i i, and in operativerelation therewith, the press is equipped with the conventionaldampening mechanism it and inking mechanism it, the former of whichmechanism serves for applying a film of ink repelling substance to thenon-design portions of the plate ll before the form rollers of theinking mechanism are brought into contact with the plate in order to inkits design portions.

The peripheries of the bearers on the impression cylinder it, platecylinder it and blanket cylinder it are denoted by reference numeralsit, i l and iii respectively. These peripheries also correspond with thepitch lines of the gears which, as indicated'above, are provided on eachone of said cylinders.

As indicated above, instead of applying the printing impression from theplate direct onto the material to be printed, in offset printing theimpression from the inked plate is first applied onto a blanket it orother resilient surface provided on the transfer or blanket cylinder it,and then transferred from said blanket to the printreceiving material.It will therefore be seen that the sheet iii receives its impressionduring its passage between the impression cylinder lt and the blanketcylinder ill. After receiving its impres-' sion, the printed sheet willbe released by the grippers if of the impression cylinder and taken overby any suitable delivery mechanism, not forming part of this inventionand therefore not shown. in order to convey it to sheet receiving meanssuch as a delivery table. r

In order to illustrate the above referred to condition that is set up atthe printing zone i. e. at the point of contactbetween a hard impressionsurface and a soft surfaced printing member when under pressure, I haveshown in Figure 2' how the soft material on the printing member becomesdisplaced and thereby increases the effective radius of said member inthe printing zone.

In this figure the radius R represents the normal overall radius of theroller D. Assuming that the roller D is rotated in a clockwisedirection, as viewed in Figure 2, and rolled under pressure over a hardsurface A, then therubber coating B at the zone of contact with the hardsurface A will undergo a deformation and the displaced rubber willbecome deflected to the right. Therefore it will be seen that due to thedisplacement of rubber, the normal radius R has become increased toassume a dimension R.

It is evident, therefore, that as a result of the displaced rubber, theeffective radius of the roller- A similar condition develops when two ormore rollers, traveling at the same surface speed, but one having aresilient surface, are rolled together under pressure. This example Ihave illustrated in Figure 3, in which an impression cylinder it and aplate cylinder it are in simultaneous rolling contact under pressurewith a blanket cylinder it. These cylinders, the overall diameters of awhich are equal, and the bearers of which arein rolling contact, rotatein the direction of the arrows and are geared together, as indicated inFigure 5, so that their respective surface speeds are the same, ameasure which is common practice in conventional offset pressesheretofore built.

In order to obtain an impression from the plate cylinder it onto theblanket cylinder it and then from the latter onto the material whichpasses between the blanket cylinder and impression cyl-' inder, it isnecessary to apply a certain amount of squeeze between the cooperatingpairs of cylinders. Thereforaunder printing conditions, the rubberblanket it on the cylinder is undergoes a transformation at the zones ofcontact with the cylinders it and Ni so that at the printing points ofthe cylinders the effective radius of the blanket cylinder it will be Rand consequently the surface speed of that cylinder at the printing zoneis greater than the surface speed of the cylinders it? and it. Inasmuchas all of these cylinders are geared together in a manner to preventbacklash as is well known in the art, and are driven positively at a 1to 1 ratio, it is obvious that due to the increased effective radius ofthe blanket cylinder it, there must be slippage between the cooperatingcylinders at their respective zones of contact.

In order to explain the effect of such slippage on the printingcondition, I will deal separately with each rolling pair of cylinders.The first pair to be considered is the plate cylinder it and the lanketcylinder it, the surfaces of which during printing are in direct rollingcontact, because the blanket on the cylinder it is to receive an impression direct from the inked plate on the cylinder i l. Planographicplates such as are commonly used in direct as well as in offset lithography have a grained surface which carries a design or image usuallyproduced by means of a halftone screen so that'the design is made up ofequally spaced infinitesimal dots varying in area according to the depthof the tone to be printed.

It will be understood, therefore, that the slightest slippage betweenthe plate, i. e. these dots, and the surface to which the design made upby these dots is to be transferred, causes an elongation of theprinteddot as well as other undesirable defects, such as for examplesmudging of the design to be printed, premature wear of said dots on theplate. as well as of the grained non-design portionof the plate,distortion of the image, i. e. change in the dimensional proportions ofthe original design, loss of register, etc.

The condition prevailing between the second rolling pair of cylinders,see particularly Figure 4, namely the impression cylinder i3 and theblanket cylinder iii, while similar in principle, adds another factor tothese applying in connection with the first rolling pair discussedabove.

The difference involved is due to the fact that the second rolling pairfunctions to transfer the impression from the blanket It to the printreceiving material during the latters passage between the blanketcylinder and the impression cylinder. Assuming that, due to the increaseof the radius at the printing zone of the blanket cylinder ill, theeflective periphery of that cylinder has increased 5 per cent, ascompared with its normal periphery, which latter is equal to that of thecooperating plate and impression cylinders, then a slippage of 5 percent of the material to be printed will occur during each revolution.This slippage of the material may all take place with relation to eitherone of the two cylinders, or it may be divided between them, that is tosay, the material may to some extent slip on the blanket and to someextent on the impression cylinder. If there is any slippage between thematerial and the blanket, then during the transferring of the impressionto the material, further smudging of the design will result, but in theopposite direction, so that possibly the impression on the material willprint short as compared with the impression on the blanket, which waspreviously transferred thereto from the plate cylinder.

On the other hand, however, if the material follows the blanket andthereby assumes the increased surface speed developed at the printingzone, as explained above, then all the slippage of ie material will beconfined to the impression cylinder surface, and as a result there willbe less smudging, but the impression will print long on the material.

In Figure 4 I have also indicated how the internal structure of therubber blanket is distorted under printing conditions. At position a,the radius R is undisturbed, at position b the rubber undergoes a slightdistortion and due to the displaced rubber accumulated at that point,the effective radius increases, while at position 0 the rubber is almostfully compressed. This condition brings about a conflict between thenatural speed of rolling and the normal surface speed of 'the rollingcylinders as imparted by the gear drive. As a result, slippage occursand thus a volume of rubber will build up on the entering side of thecylinders in rolling contact.

In order to establish a definite range of packing thicknesses for thecylinders of different sized presses, I have developed and applied inpractice a formula which gives the correct thickness of packings for allsizes of the cylinders.

This formula shows that for instance in an offset press in which thediameter of the cylinder bearers is 20 inches, the plate cylinderdiameter should be increased .010 inch over the bearer diameter, theblanket cylinder diameter .006 inch under its bearer, and the impressioncylinder diameter .010 inch over the bearer diameter of the cylinder,allowing for a squeeze of .004 inch.

For a smaller size press in which the cylinder bearer diameter is 8inches, the packing dimensions are as follows: plate cylinder .005 inchover the bearer, blanket cylinder .001 inch under the bearer, andimpression cylinder .005 inch over the bearer.

At first these dimensions seem extremely excessive and quitecontradictory to any packing methods heretofore used on offset presses,particularly so because, according to my formula, the modified diameterover-all of the blanket cylinder is appreciably less than the diameterof the blanket cylinder bearer. However, the congruity and accuracy ofthis formula has been fully substantiated by numerous tests which wererun under actual commercial printing conditions, and which have provenbeyond any doubt that by my method of packing the cylinders, anabsolutely true rolling contact is established and maintained at theprinting zone of complementary cylinders. It is therefore evident thatmymethod is based on actual facts developed during a period of longexperimentaton, and that by means of my formula I can definitelyascertain the accurate packing dimensions for offset presses of anysize.

It is also of importance to note that by dimensioning the cylinders astaught by mymethod, the bearers of all the complementary cylinders willremain in rolling contact under printing conditions. Heretofore it hasbeen quite common that during printing, the complementary cylinderswould not ride on their respective bearers, a condition evidently due toincorrect packing methods.

I also wish it to be understood that the formula by means of which Ihave obtained the above figures is based on commercially standardqualities of rubber blankets, and that these figures may vary slightlywhen either softer or harder quality blankets are used.

While the conditions set forth herein could be substantiated in moredetail by elaborate discussions of the theoretical points involved, Ibelieve that the illustrations given and the facts pointed out abovefurnish sufficient proof in support of the contention that in order toestablish true rolling conditions between the cooperating printingmembers, it is essential that under printing conditions, the surfacespeed of all said members at the printing zone be identical.

It will also be understood that while I prefer to accomplish the desiredresult by suitably dimensioning the diameters of the respective rollingpairs of printing members, the same effect could be obtained by anyother method whereby the surface speed at the printing zone between suchmembers can be equalized and maintained the same during printingconditions.

Furthermore, it will be evident that while I have illustrated anddescribed my method of printing as applied in connection with aplanographic printing press, it could be equally well used in connectionwith any other type of printing press where similar conditions are setup between the printing couples when the press is in operation.

I claim:

1. In a printing press, the combination of cooperating form and blanketcylinders having relatively hard and soft operating surfaces whereby aprinting impression is conveyed from one to the other, each of saidcylinders having engaging bearers, said blanket cylinder having itsimpression receiving surface below its bearers and the form cylinderhaving its active surface above its bearers whereby said surfaces at theprinting zone travel at the same speed to transfer a true imageundistorted.

2. In a printing press, the combination of cooperating form, blanket andimpression cylinders having relatively hard and soft operating surfaceswhereby a printing impression is conveyed from said form cylinder tosaid blanket cylinder and from the latter to material passed betweensaid blanket and impression cylinders, each of said cylinders havingengaging bearers, said blanket cylinder having its impression receivingsurface below its bearers, and said form and impression cylinders havingtheir active surfacesv above their bearers, whereby all of said surfacesat the printing zone travel at the same speed to transfer a true imageundistorted.

3. In a printing press, the combination of cooperating blanket andimpression cylinders having relatively hard and soft operating surfaceswhereby a printing impression is conveyed from said blanket cylinder tomaterial passed between the latter and said impression cylinder, each ofabsence said cylinders having engaging bearers, said blanket cylinderhaving its impression receiving surface below its bearers and saidimpression cylinder having its active surface above its bearers wherebysaid surfaces at the printing zone travel at the same speed to transfera true image undistorted.

4.-. In a printing press, the combination of cooperating form, blanketand impression cylinders having relatively hard and soft operatingsurfaces whereby a printing impression is conveyed from said formcylinder to said blanket cylinder and from the latter onto materialpassed between it and said impression cylinder, said form and impressioncylinders being so ,dimensioned that their surface speeds will begreater than the peripheral speed of their corresponding bearers, whilesaid blanket cylinder is so dimensioned that its surface speed will beless than the peripheral speed of its bearers.

5. In an offset press, a plate cylinder in which the printing surface israised between .004 inch and .040 inch above the normal pitch line ofits gear, a blanket cylinder in which the surface of the resilientblanket is depressed between .004

inch and .036 inch below the pitch line of the I blanket cylinder gear,and an impression cylinder in which the impression surface is arrangedso that the surface of the material receiving the impression is from.004 inch to .040 inch above the normal pitch line of the impressioncylinder gear.

6. The method of printing with a press having a plurality ofcooperating, relatively hard and soft surfaced printing members, havingbearers associated therewith, consisting in so dimensioning the softsurfaced one of said members that its operating surface will be belowits bearers, dimensioning the hard surfaced cooperating member ormembers so that the operating surface of each will be above the bearers,and applying printing pressure to said members to thereby establish truerolling condition between said printing members.

member having its active surface above its bearers, the proportionatedimensioning of said members being such that under printing conditionsaid surfaces at the printing zone travel at the same speed to transfera true image undistorted.

8. In a printing press, the combination of operating form and blanketcylinders having relatively hard and soft operating surfaces whereby aprinting impression is conveyed from one to the other, each of saidcylinders having engaging bearers of equal diameters to thereby producetrue rolling contact between said bearers, said blanket cylinder havingits impression receiving surface below its bearers and said formcylinder having its active surface above its bearers, the

diameters of said cylinders being so dimensioned 1 impression receivingsurface below its bearers and said form cylinder having its activesurface above its bearers, the diameters of said cylinders being sodimensioned that under printing condition said surfaces at the printingzone travel at the same speed to transfer a true image undistorted.

10. In a printing press, the combination of co- 7 operating form andblanket cylinders having relatively hard and soft operating surfaceswhereby a printing impression is conveyed from one to the other, saidcylinders being geared together and having engaging bearers, thediameters of said bearers being equal to the pitch line diameters of thegears associated with said cylinders, said blanket cylinder having itsimpression receiving surface below its bearers and said form cylinderhaving its active surface above its bearers, the diameters of saidcylinders being so dimensioned that under printing condition saidsurfaces at the printing zone travel at the same speed to transfer atrue image undistorted.

11. In a printing press,'the combination of cooperating form, blanketand impression cylinders having relatively hard and soft operatingsurfaces whereby a printing impression is conveyed from one to theother, said cylinders being geared together and having engaging bearers,the diameters of said bearers being equal to the pitch line diameters ofthe gears associated with said cylinders, said blanket cylinder havingits impression receiving surface below its bearers and said form andimpression cylinders having their active surfaces above their bearers,the diameters of said cylinders being so dimensioned that under printingcondition said surfaces at the printing zone travel at the same speed totransfer a true image undistorted.

BENJ.

1 L. SITES.

